Tracking the Light-Induced Excited-State Dynamics and Structural Configurations of an Extraordinarily Long-Lived Metastable State at Room Temperature - Iglesias, Sirma; Gamonal, Arturo; Abudulimu, Abasi; Picon, Antonio; Carrasco, Esther; Ecija, David; Liu, Cunming; Luer, Larry; Zhang, Xiaoyi; Costa, Jose Sanchez; Moonshiram, Dooshaye (Chemistry - A European Journal, 2020)
Time-resolved X-ray (Tr-XAS) and optical transient absorption (OTA) spectroscopy on the pico-microsecond timescale coupled with density functional theory calculations are applied to study the light-induced spin crossover processes of a Fe-based macrocyclic complex in solution. Tr-XAS analysis after light illumination shows the formation of a seven-coordinated high-spin quintet metastable state, which relaxes to a six-coordinated high-spin configuration before decaying to the ground state. Kinetic analysis of the macrocyclic complex reveals an unprecedented long-lived decay lifetime of approximately 42.6 μs. Comparative studies with a non-macrocyclic counterpart illustrate a significantly shortened approximately 568-fold decay lifetime of about 75 ns, and highlight the importance of the ligand arrangement in stabilizing the reactivity of the excited state. Lastly, OTA analysis shows the seven-coordinated high-spin state to be formed within approximately 6.2 ps. These findings provide a complete understanding of the spin crossover reaction and relaxation pathways of the macrocyclic complex, and reveal the importance of a flexible coordination environment for their rational design.
CRIS-Team Scopus Importer:2020-08-14
Keywords: density functional calculations; excited state structures; iron spin crossover complexes; optical transient absorption spectroscopy; spin crossover

Tuning Interactions to Control Molecular Down Conversion in [2.2]Paracyclophane Bridged Oligo-Tetracenes - Rapp, Mario R.; Weiß, René; Wollny, Anna-Sophie; Guldi, Dirk Michael; Bettinger, Holger F. (Advanced Functional Materials, 2024)
In tetracene, the energies of the lowest singlet excited state and twice that of the lowest triplet excited state are similar, allowing both down-conversion (i.e., singlet fission, SF) and up-conversion (i.e., triplet-triplet annihilation up-conversion, TTA-UC) processes. Through-space and through-bond contributions to the inter-tetracene coupling in purposefully designed oligomers play a crucial role in determining which of the two processes dominates. In this work, the focus is exclusively on SF in newly synthesized oligo-tetracenes linked by conjugated [2.2]paracyclophane (PCP) building blocks. By choosing different PCP substitution patterns and by varying the degree of substitution the inter-tetracene couplings are addressed. An independent variable is connecting the tetracences to the PCP at different positions to alter the through-bond and through-space coupling of the resulting oligo-tetracenes. The novel oligo-tetracenes are investigated by means of steady-state and time-resolved absorption and fluorescence spectroscopies with respect to the initial events of SF, that is, the transformation of a singlet excited state into a correlated triplet pair state. Briefly, through-space couplings are profoundly weaker than through-bond couplings that enable the correlated triplet pair state formation. If interactions are through-space, correlated triplet pair state formation is turned off, while it is turned on if through-bond interactions are operative.
CRIS-Team Scopus Importer:2024-03-15
Keywords: acenes; cyclophanes; excited states; oligomers; photophysics; singlet fission

Ultrafast electronic relaxation pathways of the molecular photoswitch quadricyclane - Borne, Kurtis D.; Cooper, Joseph C.; Ashfold, Michael N. R.; Bachmann, Julien; Bhattacharyya, Surjendu; Boll, Rebecca; Bonanomi, Matteo; Bosch, Michael; Callegari, Carlo; Centurion, Martin; Coreno, Marcello; Curchod, Basile F. E.; et al. (Nature Chemistry, 2024)
The light-induced ultrafast switching between molecular isomers norbornadiene and quadricyclane can reversibly store and release a substantial amount of chemical energy. Prior work observed signatures of ultrafast molecular dynamics in both isomers upon ultraviolet excitation but could not follow the electronic relaxation all the way back to the ground state experimentally. Here we study the electronic relaxation of quadricyclane after exciting in the ultraviolet (201 nanometres) using time-resolved gas-phase extreme ultraviolet photoelectron spectroscopy combined with non-adiabatic molecular dynamics simulations. We identify two competing pathways by which electronically excited quadricyclane molecules relax to the electronic ground state. The fast pathway (<100 femtoseconds) is distinguished by effective coupling to valence electronic states, while the slow pathway involves initial motions across Rydberg states and takes several hundred femtoseconds. Both pathways facilitate interconversion between the two isomers, albeit on different timescales, and we predict that the branching ratio of norbornadiene/quadricyclane products immediately after returning to the electronic ground state is approximately 3:2.<br
Keywords: Chemical physics; Photochemistry

Unlocking the potential of digitalization and automation: a qualitative and quantitative study of the control cabinet manufacturing industry - Bründl, Patrick; Stoidner, Micha; Bredthauer, Jens; Nguyen, Huong Giang; Baechler, Andreas; Franke, Jörg (Production & Manufacturing Research, 2024)
This paper investigates the German control cabinet manufacturing industry, revealing its opportunities, challenges, and varying levels of digitalization and automation. The researchers employ cluster analysis, grouping companies into five clusters based on digitalization and automation, resulting in a new classification framework. This framework significantly improves the similarity level within each cluster by approximately 52.89 % compared to pre-existing models. While the levels of digitalization and automation vary greatly between the different clusters, skill shortages and supply chain problems are identified as potential development barriers to companies from all groups. To overcome these obstacles, the paper outlines key improvement areas based on data findings. This proposed classification can guide companies in assessing their digital maturity and pinpointing enhancement areas, emphasizing the necessity of adopting digitalization and automation for improved efficiency and market competitiveness.<br
CRIS-Team Scopus Importer:2024-02-02
Keywords: Control cabinet; digitalization; production automation; production strategies; engineer-to-order production

Unveiling the Multielectron Acceptor Properties of π-Expanded Pyracylene: Reversible Boat to Chair Conversion - Zhu, Yikun; Borstelmann, Jan; Bertleff, Oliver; Bergner, John; Wei, Zheng; Neiß, Christian; Görling, Andreas; Kivala, Milan; Petrukhina, Marina A. (Journal of the American Chemical Society, 2024)
In this work, the chemical reduction of a hybrid pyracylene-hexa-peri-hexabenzocoronene (HPH) nanographene was investigated with different alkali metals (Na, K, Rb) to reveal its remarkable multielectron acceptor abilities. The UV-vis and 1H NMR spectroscopy monitoring of the stepwise reduction reactions supports the existence of all intermediate reduction states up to the hexaanion for HPH. Tuning the experimental conditions enabled the synthesis of the HPH anions with gradually increasing reduction states (up to −5) isolated with different alkali metal ions as crystalline materials. The single-crystal X-ray diffraction structure analysis demonstrates that the highly negatively charged HPH anions (−4 and −5) exhibit a drastic geometry change from boat-shaped (observed in the neutral parent, mono- and dianions) to a chair conformation, which was proved to be fully reversible by NMR spectroscopy. DFT calculations show that this geometry change is induced by an enhanced interaction between the coordinated metal ions and negatively charged HPH core in the chair conformation.
CRIS-Team Scopus Importer:2024-05-24
Keywords: Conformation; Ethers; Ions; Redox reactions; Transfer reactions

Use of printed sensors to measure strain in rolling bearings under isolated boundary conditions - Bartz, Marcel; Halmos, Fabian; Jüttner, Michael; Ankenbrand, Markus; Häusler, Felix; Franke, Jörg; Wartzack, Sandro (Konstruktion, 2024)

Valence shell electronically excited states of norbornadiene and quadricyclane - Cooper, Joseph C.; Holland, David M. P.; Ingle, Rebecca A.; Bonanomi, Matteo; Faccialà, Davide; De Oliveira, Nelson; Abid, Abdul R.; Bachmann, Julien; Bhattacharyya, Surjendu; Borne, Kurtis D.; Bosch, Michael; Centurion, Martin; et al. (Journal of Chemical Physics, 2024)
The absolute photoabsorption cross sections of norbornadiene (NBD) and quadricyclane (QC), two isomers with chemical formula C7H8 that are attracting much interest for solar energy storage applications, have been measured from threshold up to 10.8 eV using the Fourier transform spectrometer at the SOLEIL synchrotron radiation facility. The absorption spectrum of NBD exhibits some sharp structure associated with transitions into Rydberg states, superimposed on several broad bands attributable to valence excitations. Sharp structure, although less pronounced, also appears in the absorption spectrum of QC. Assignments have been proposed for some of the absorption bands using calculated vertical transition energies and oscillator strengths for the electronically excited states of NBD and QC. Natural transition orbitals indicate that some of the electronically excited states in NBD have a mixed Rydberg/valence character, whereas the first ten excited singlet states in QC are all predominantly Rydberg in the vertical region. In NBD, a comparison between the vibrational structure observed in the experimental 11B1–11A1 (3sa1 ← 5b1) band and that predicted by Franck–Condon and Herzberg–Teller modeling has necessitated a revision of the band origin and of the vibrational assignments proposed previously. Similar comparisons have encouraged a revision of the adiabatic first ionization energy of NBD. Simulations of the vibrational structure due to excitation from the 5b2 orbital in QC into 3p and 3d Rydberg states have allowed tentative assignments to be proposed for the complex structure observed in the absorption bands between ∼5.4 and 7.0 eV.<br
Keywords: Photoabsorption; Synchrotron radiation; Ions and properties; Isomerism; Absorption spectroscopy; Oscillator strengths; Organic compounds; Chemical compounds; Absorption band; Rydberg states

Which Comprehensive Geriatric Assessment (CGA) instruments are currently used in Germany: a survey - Kudelka, Jennifer; Ollenschläger, Malte; Dodel, Richard; Eskofier, Björn; Hobert, Markus A.; Jahn, Klaus; Klucken, Jochen; Labeit, Bendix; Polidori, M. Cristina; Prell, Tino; Warnecke, Tobias; von Arnim, Christine A.F.; et al. (BMC Geriatrics, 2024)
Background: The Comprehensive Geriatric Assessment (CGA) records geriatric syndromes in a standardized manner, allowing individualized treatment tailored to the patient’s needs and resources. Its use has shown a beneficial effect on the functional outcome and survival of geriatric patients. A recently published German S1 guideline for level 2 CGA provides recommendations for the use of a broad variety of different assessment instruments for each geriatric syndrome. However, the actual use of assessment instruments in routine geriatric clinical practice and its consistency with the guideline and the current state of literature has not been investigated to date. Methods: An online survey was developed by an expert group of geriatricians and sent to all licenced geriatricians (n = 569) within Germany. The survey included the following geriatric syndromes: motor function and self-help capability, cognition, depression, pain, dysphagia and nutrition, social status and comorbidity, pressure ulcers, language and speech, delirium, and frailty. Respondents were asked to report which geriatric assessment instruments are used to assess the respective syndromes. Results: A total of 122 clinicians participated in the survey (response rate: 21%); after data cleaning, 76 data sets remained for analysis. All participants regularly used assessment instruments in the following categories: motor function, self-help capability, cognition, depression, and pain. The most frequently used instruments in these categories were the Timed Up and Go (TUG), the Barthel Index (BI), the Mini Mental State Examination (MMSE), the Geriatric Depression Scale (GDS), and the Visual Analogue Scale (VAS). Limited or heterogenous assessments are used in the following categories: delirium, frailty and social status. Conclusions: Our results show that the assessment of motor function, self-help capability, cognition, depression, pain, and dysphagia and nutrition is consistent with the recommendations of the S1 guideline for level 2 CGA. Instruments recommended for more frequent use include the Short Physical Performance Battery (SPPB), the Montreal Cognitive Assessment (MoCA), and the WHO-5 (depression). There is a particular need for standardized assessment of delirium, frailty and social status. The harmonization of assessment instruments throughout geriatric departments shall enable more effective treatment and prevention of age-related diseases and syndromes.
CRIS-Team Scopus Importer:2024-04-26
Keywords: Activities of daily living; CGA; Cognition; Comorbidities; Comprehensive geriatric assessment; Delirium; Depression; Dysphagia; Frailty; Self-help capability